title: Inhibitory action of hydrogen sulfide on muscarinic receptor-induced contraction of isolated porcine irides.
abstract: We investigated the pharmacological actions of hydrogen sulfide (H(2)S) using sodium hydrosulfide (NaHS) and sodium sulfide (Na(2)S) as donors on isolated porcine irides in the presence of tone induced by muscarinic receptor stimulation. Furthermore, we also investigated the mechanism of action of H(2)S in this smooth muscle. Isolated porcine iris muscle strips were set up in organ baths and prepared for measurement of longitudinal isometric tension. The relaxant action of NaHS or Na(2)S on carbachol-induced tone was studied in the absence and presence of a K(+)-channel inhibitor and inhibitors/activators of enzymes of the biosynthetic pathways for H(2)S, prostanoid and nitric oxide production. In the concentration range, 10 nM to 100 microM, NaHS produced a concentration-dependent relaxation of carbachol-induced tone reaching a maximum of inhibition of 28% at 30 microM. The cyclooxygenase inhibitor, flurbiprofen (1 microM), enhanced relaxations induced by both NaHS and Na(2)S yielding IC(50) values of 7 microM and 70 microM, respectively. With exception of l-NAME (300 muM) inhibitors of cystathionine gamma-lyase, propargylglycine, (PAG) (1 mM) and beta-cyanoalanine, (BCA) (1 mM) and inhibitors of cystathionine beta-synthase, aminooxyacetic acid (AOA) (30 microM) and hydroxylamine (HOA) (30 microM) caused significant (P < 0.001) rightward shifts in the concentration-response curves to NaHS. An activator of cystathionine beta-synthase, SAM (100 microM), enhanced relaxations elicited by low concentrations of NaHS but attenuated responses caused by the higher concentrations of this H(2)S donor. The inhibitor of K(ATP) channel, glibenclamide (100 and 300 microM), blocked relaxations induced by NaHS. We conclude that the observed inhibitory action of NaHS and Na(2)S in isolated porcine irides is dependent on endogenous production of prostanoids and the biosynthesis of H(2)S by cystathionine gamma-lyase and cystathionine beta-synthase. Furthermore, relaxation induced by H(2)S is mediated, at least in part, by K(ATP) channels. Nitric oxide is not involved in the relaxation induced by this gas in the isolated porcine irides.
authors.affiliation: Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, USA.
authors.forename: Emmanuel M
authors.initials: EM
authors.lastname: Monjok
authors.forename: Kaustubh H
authors.initials: KH
authors.lastname: Kulkarni
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Kouamou
authors.forename: Marshalyn
authors.initials: M
authors.lastname: McKoy
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Opere
authors.forename: Odelia N
authors.initials: ON
authors.lastname: Bongmba
authors.forename: Ya Fatou
authors.initials: YF
authors.lastname: Njie
authors.forename: Sunny E
authors.initials: SE
authors.lastname: Ohia
mesh_terms: D000818:Animals; D002217:Carbachol / Q000037:antagonists & inhibitors / Q000494:pharmacology; D003541:Cystathionine beta-Synthase / Q000502:physiology; D003542:Cystathionine gamma-Lyase / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006862:Hydrogen Sulfide / Q000494:pharmacology*; D007498:Iris / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D054086:KATP Channels / Q000502:physiology; D008916:Miotics / Q000037:antagonists & inhibitors / Q000494:pharmacology; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009569:Nitric Oxide / Q000502:physiology; D009924:Organ Culture Techniques; D011976:Receptors, Muscarinic / Q000502:physiology; D034421:Sus scrofa
chemical_list: D054086:KATP Channels; D008916:Miotics; D018727:Muscarinic Antagonists; D011976:Receptors, Muscarinic; D009569:Nitric Oxide; D002217:Carbachol; D003541:Cystathionine beta-Synthase; D003542:Cystathionine gamma-Lyase; D006862:Hydrogen Sulfide